Corporate Records

Many early applications concerned corporate records, such as a record of each sale, information about accounts payable and receivable, or information about employees - their names, addresses, salary, benefit options, tax status, and so on. Queries comprise the printing of reports such as accounts receivable or employee's weekly paychecks. Each sale, purchase, bill, receipt, employee hired, fired, or promoted, and so on, results in a modification to the database.

The early DBMS's, developing from file systems, encouraged the user to visualize data much as it was stored. These database systems used a number of different data models for describing the framework of the information in a database, chief among them the "hierarchical" or tree-based model and the graph-based "net-work" model. The latter was standardized in the late 1960's through a report of CODASYL (Committee on Data Systems and Languages).

A problem with these early models and systems was that they did not support high-level query languages. For example, the CODASYL query language had statements that allowed the user to jump from data element to data element, through a graph of pointers among these elements. There was much effort needed to write such programs, even for very simple queries.